Method and apparatus for forming cross ribbed pipes

Abstract

A method and apparatus of forming ribbed pipes, after an initial pipe resssing in which bending of the rib of the plane perpendicular to the rolled pipe axis takes place, and straightening of the rib thenafter. Then on duplex metal pipes, the outside pipe is additionally compressed to the core pipe. A tool for performing the aforementioned is equipped with a disk section for bending the rib, it is formed of a thrust disk and a straightening disk. When rolling a duplex metal pipe at least one compressing disk is placed therebetween.

We claim: 
     
       1. A method of forming cross ribbed pipes of duplex metal structure in a rolling process by pinching action on the pipe surface, initial rib extending and forming the rib shape, comprising the steps of: initially restressing a formed pipe rib; bending said pipe rib several times out of a plane perpendicular to a rolling axis by simultaneously compressing said ribbed pipe to a core pipe, and straightening said rib. 
     
     
       2. A method of forming cross ribbed pipes of simple metallic structure by rolling, including pinching the pipe surface, initial rib extending and forming a rib shape, and comprising the steps of: forming a pipe rib by bending said rib out of the plane perpendicular to the rolling axis, and then straightening said rib. 
     
     
       3. A tool for forming cross ribbed pipes of duplex metal structure, employing symmetrical disks arranged in sections adapted to pinch a surface of said pipe, initially extend and forming the rib shape, wherein: said tool being defined by an additional section of asymmetrical rolling disks for rib bending on both sides, said tool comprising: a thrust disk having the first of its faces in the rolling direction in a shape corresponding to a last forming disk profile, and its second face tapered to a cone angle of 140° to 170°; at least one compressing disk apart of said thrust disk at 2 to 6 rib pitches, having one face tapered to a cone angle of 155° to 170°, another face flat, whereby the first of said compressing disks has said tapered face directed opposite to a pipe feed direction and subsequent compression disks being alternatively arranged; said compressing disks being formed with outside diameters a little larger that said diameters of the last forming disks; a straightening disk with one face in rolling direction tapered to having a cone angle of 155° to 170° and its rear face corresponding to last forming disk profile. 
     
     
       4. A tool for forming cross ribbed pipes of simple metal structure employing symmetrical disks arranged in sections for pinching of pipe surfaces, initial rib extending and forming a rib shape, wherein: said tool being defined by an additional section of asymmetrical disks for rib bending, said tool comprising: a thrust disk having the first of its faces in a rolling direction of a shape corresponding to the last forming disk profile, and its second face tapered to a cone angle of 140° to 170°; a straightening disk, facing the pipe feed having its side tapered to a cone angle of 155° to 170° and having its rear face corresponding to the last forming disk profile.